1. Field of the Invention
One or more embodiments of the present invention relates to an apparatus for collecting contaminating particles included in an air flow with a plurality of cyclones, and particularly relates to a multi-cyclone collector suitable for separating and collecting oil mist generated during processing of a machine tool.
2. Background Art
Conventional collectors for separating and collecting oil mist include filter apparatuses for filtrating with nonwoven fabric. However, the nonwoven fabric causes clogging and its processable air volume is reduced gradually in the course of time. Maintenance or replacement of the nonwoven fabric is thus required uneconomically. In view of this, collectors commercially available in recent years are so-called filterless collectors for separating and collecting oil mist not by filtration but with inertial force, centrifugal force, or the like. However, many of these collectors fail in highly accurate separation and exert insufficient collection performance. Therefore, improvement in performance of the filterless collectors is urgently needed for better economic efficiency and work environment.
A cyclone is one of devices that are capable of separating contaminating particles such as dust and oil mist with high accuracy. As schematically shown in FIG. 20, the cyclone transforms a contaminated air flow taken therein to a swirl flow, applies centrifugal force to contaminating particles in the air flow, separates the contaminating particles from the air flow with the centrifugal force, and releases a purified air flow including no contaminating particles. The cyclone of this type has larger centrifugal force as the swirl flow has a smaller swirl radius (cyclone radius). This leads to decrease in separable particle diameter (so-called separation limit particle diameter) and enables highly accurate separation.
The filterless collectors also adopt cyclones. However, a conventional cyclone has a large cyclone radius and low separation accuracy, and is thus utilized as preprocessing devices. The collector needs to include, after the cyclone, a collection mechanism such as a filter having a finer structure. In this case, there arise disadvantages such as clogging and large pressure loss (see Patent Literatures 1 to 3, for example).
A cyclone is restricted due to so-called similarity in design, and decrease in cyclone radius inevitably leads to decrease in size of an inlet port for an air flow. Consequently, if the air flow has constant speed, processable air volume is decreased. In view of this, there has been known a multi-cyclone collector including a plurality of cyclones aligned in parallel so as to achieve necessary air volume even with a small cyclone radius (see Patent Literatures 4 to 6, for example).